1. Field of the Invention
The present invention relates to a multi-column electron beam exposure apparatus and a magnetic field generation device, and particularly relates to a multi-column electron beam exposure apparatus and a magnetic field generation device which are capable of generating a strong magnetic field in a small space so that the intervals between column cells can be made small.
2. Description of the Related Art
For the purpose of improving throughput, an electron beam exposure apparatus is provided with a variable rectangular aperture or multiple stencil mask patterns (character projection (CP)) in a stencil mask, and transfers a desired pattern onto a wafer through exposure by selectively using the aperture or patterns with beam deflection.
As an example of such electron beam exposure apparatuses, Japanese Laid-Open Patent Publication No. 2004-88071 discloses an electron beam exposure apparatus for character projection lithography. In the character projection lithography, one pattern region of, for example, 20×20 μm is selected through beam deflection from a mask where multiple (e.g., 100) stencil patterns are arranged, and irradiated with a beam so that the beam can be formed to have a cross section in the shape of the stencil pattern. Further, the beam having passed through the mask is deflected back by a downstream deflector and reduced in size at a given reduction rate determined by the electron optical system (e.g., 1/10). The shape of the stencil pattern is then transferred onto a sample. If the stencil patterns in the mask are prepared as appropriate in accordance with the device pattern for exposure, the number of required exposure shots is reduced greatly and the throughput is improved, as compared to the case of using only a variable rectangular aperture.
There has also been proposed a multi-column electron beam exposure apparatus which includes multiple small-sized columns (referred to as “column cells” below) of such exposure apparatuses and performs exposure processing in parallel using the multiple column cells arranged above a wafer. Each of the column cells is equivalent to a column of a single-column electron beam exposure apparatus. Since the multi-column electron beam exposure apparatus performs the exposure processing by multiple column cells in parallel, exposure throughput of the multi-column electron beam exposure apparatus as a whole can be multiplied by the number of columns.
However, use of the multiple column cells as above entails involves the following limitations. The size of the character projection mask usable in the multi-column method is restricted to 150 mm2 or smaller due to the nature of the manufacturing thereof. Also, the mask of such a large size as around 300 mm2 is unacceptable in consideration of the handling and storing of CP masks and wafers. Thus, the multiple column cells need to be arranged within a region of 150 mm2 or smaller. In this case, the pitch of the column cells is 50 mm, 30 mm, 25 mm or the like, which is a result of division of 150 mm by a certain integer. For this reason, coils used in the electromagnetic lenses for converging electron beams need to be reduced in size. Measures, such as using coil wires of smaller diameters, may be employed to reduce the sizes of the coils. However, such measures may increase the amounts of heat generated by the coils, and possibly break the coils.